This invention essentially relates to the use of an ultrasound echography device operating in A-mode for monitoring the position of a patient during a therapy session, and to a method and apparatus applying it.
It is known that focused ultrasound can be used for treating tumors. Generally, this is done in several stages, and more specifically consists in first locating the volume to be treated, then calculating the firing positions and after this directing successive shots to the calculated positions.
In accordance with known methods, the shot is either done xe2x80x9cblindxe2x80x9d or sometimes advantage is taken of the vacant period between shots for providing an ultrasound image for monitoring purposes.
Treatment that is done xe2x80x9cblindxe2x80x9d can be dangerous as the sessions are frequently long and the patientxe2x80x94even if anesthetizedxe2x80x94may well move. In this case, there is a danger of damaging healthy or even vital parts.
Thus, by providing an image, the actual position of the therapeutic transducer with respect to organs close to the target can be monitored. However, this method does not offer absolute safety as one cannot be sure that the medical personnel will pay sustained attention to the screen displaying the ultrasound image throughout the whole duration of the treatment. Image analysis techniques have been proposed in order to overcome this disadvantage but these require specific and highly complex electronic systems and software which increases the cost of equipment and can be the source of additional problems.
Another disadvantage of this solution resides in the actual ultrasound scan itself. The system used may be conventional in the sense that it includes an ultrasound scanning head as described in International application WO 92/15253. This document discloses the incorporation of an ultrasound scanning head into a therapy transducer, but this means that the head masks a portion of the therapy transducer thus reducing the effectiveness of the apparatus, as is pointed out in said application where it is indicated that one always attempts to maximize the transmission surface area of the therapy transducer.
It is also possible to obtain an ultrasound image of the target and the area surrounding it without reducing the transmission surface area of the therapy transducer. This is achieved by using a transducer element connected to B-type scan apparatus as described in IEEE 1992 Ultrasonics Symposium Proceedings, in an article by N. T. Sanghyi, R. S. Foster, F. J. Fry, R. Birhle, C. Hennige and L. V. Hennige entitled xe2x80x9cUltrasound intracavitary system for imaging, therapy and planning, and treatment of focal diseasesxe2x80x9d, pages 1,249 to 1,253. For each position of the therapy transducer head, one line of the image will be obtained. In order to obtain the complete image, it is thus necessary to move the therapy head sequentially. This is a slow process as the image rate is limited by the mechanical scanning of the therapy head.
Moreover, before it was known how to produce an image with B-mode scanning equipment, A-mode echography was employed either for measuring distance, for example in echography of the eye, or for measuring the degree of opening of mitral valves, or, yet again, for measuring and locating the mid-axis of the brain, or, still further, for bone positional location with a view to treatment as described in an earlier document in the name of the assignee, FR-A-2,660,186 equivalent to U.S. Pat. No. 5,235,981.
However, A-mode echography has never been employed at the actual time of therapy and even less for monitoring the position of a patient during therapy.
Additionally, to check the position of a patient during therapy, the use of luminous markers has been proposed; see FR-A-2,663,529 in the name of the present assignee; U.S. Pat. No. 4,132,900 (W. E. Smith); DE-A-2,361,155 (C. Lescrenier) and EP-A-0,260,550 (Siemens A. G.). However, luminous markers can obviously not be employed in certain cases, as is for example the case in endocavital treatment.
The present invention thus sets out to resolve the technical problem of supplying a way of reliably and accurately monitoring the position of a patient during therapy. It would be advantageous if this solution could be particularly simple.
A further aim of the invention is to provide a way of supplying an image allowing the position of a patient to be automatically monitored during therapy in a reliable, accurate and particularly simple fashion.
A further aim of the invention is to provide a way of not only monitoring the position of a patient during therapy, but also of performing correction and closed-loop control of the position either of the patient or of the therapy apparatus during therapy, so that said therapy may be correctly performed throughout the whole duration thereof. Preferably, this solution should also enable real time control of a therapy transducer to be obtained with respect to a predetermined reflecting contour this being done independently of all other traditional imaging systems.
Yet a further aim of the invention is to resolve the above technical problems while at the same time providing a way of alerting the practitioner and/or medical staff during therapy should the patient""s position inadvertently change.
This invention makes it possible to simultaneously resolve all the technical problems stated above in a safe and reliable manner that can be applied on an industrial and medical scale.
Thus, according to a first aspect, the invention provides for the use of an A-mode echography device for monitoring the position of a patient, during a therapy session.
When A-mode echography is used in this way, it is advantageous to modify the aim of the therapy apparatus as a function of movements detected by the A-mode echography device.
It can also be arranged for the A-mode echography device to interrupt therapy if it is detected that movements of the patient are above a predefined limit which may be a function of a safety margin.
According to one preferred feature, the A-mode echography device carries out real time control of the position of therapy apparatus comprising, for example, a therapy probe with respect to a predetermined reflecting contour, preferably independently of any other conventional imaging system, this being particularly simple.
For example, to take the example of treatment of the prostate, it is possible to control the therapy device which for example includes at least one therapy transducer, using the A-type echo from the rectal wall. This is performed independently of the imaging system. This makes it possible to create lesions situated at a precise distance, typically some 3 mm, from the rectum, for correct treatment. Similarly, in the case of thyroid treatment, provision can also be made to control the therapy device in real time on the basis of the echo from the trachea.
For the actual therapy, therapy apparatus using focused ultrasound is preferably employed.
According to a second aspect, this invention also provides a method for monitoring the position of a patient, in particular the position of an organ of the patient to be treated, during a therapy session including:
a) providing an ultrasound monitoring transducer operating in A-mode in acoustic contact with the patient to be monitored, in particular with an organ to be treated, the transducer being in a known position, for example fixed to a structure which, in particular, is the supporting means for said patient;
b) exiting the ultrasound monitoring transducer operating in A-mode with a brief signal in the form of a pulse, for example between shots of an apparatus providing said therapy;
c) receiving the echoes of the signal at the transducer;
d) transforming said received echoes into an electrical signal;
e) locating, in the signal corresponding to the echoes, the position or shape of a structure that is characteristic of the echo from a tissue to be monitored of the patient;
f) comparing the position or shape of the structure characteristic of the echo from a tissue to be monitored in the patient with the position or shape of a reference echo signal from tissue to be monitored of said patient; and
g) when the result of the comparison indicates a change of the position or shape of the received echo signal with respect to the reference echo signal position or shape, transmitting this information to an appropriate control device.
According to an advantageous feature, the control device triggers an alarm when information is transmitted thereto indicating a change in the position or shape of the echo signal received with respect to a reference echo signal, or even the absence of reception of said echo signal.
Advantageously, the control device performs real time closed-loop control of the position of the therapy device as a function of the movements of the patient, in particular of said organ to be treated, preferably with respect to a predetermined reflecting contour of said patient such, as the rectal wall during prostate treatment, or the trachea during thyroid treatment.
According to a further advantageous feature, the ultrasound monitoring transducer operating in A-mode is mechanical linked to the therapy device.
The therapy device preferably includes at least one ultrasound therapy transducer providing therapy using focused ultrasound.
The ultrasound therapy transducer is advantageously arranged inside balloon means filled with an acoustic coupling fluid.
Preferably, the reference echo signal corresponds to the desired distance between a highly echogenic interface, such as the interface in contact with the wall of the balloon means and the ultrasound therapy transducer, the comparison consisting of comparing the actual distance measured for the echo corresponding to said interface and the reference distance for the interface relative to said therapy transducer.
According to a preferred feature, when the measured distance is smaller than the reference distance, the therapy transducer is controlled whereby its distance with respect to the patient, in particular with respect to an organ to be treated increases, while if the measured distance is greater than said reference distance, the therapy transducer is controlled whereby its distance with respect to the patient, and in particular with respect to the organ to be treated, is decreased.
The ultrasound therapy transducer is preferably a focused ultrasound therapy transducer integrated into an endocavital probe, preferably a rectal probe, for providing treatment of benign or malignant tumors, in for providing treatment of the prostate or the thyroid, notably cancers.
Other advantageous embodiments will also become evident from the detailed description provided below that relates to the therapy apparatus and from the examples and the drawings which constitute an integral part of this disclosure.
According to a third aspect, the invention provides a therapy apparatus including a therapy device including at least one ultrasound therapy transducer and at least one monitoring ultrasound transducer, wherein said ultrasound monitoring transducer is linked to an electronic circuit for processing A-mode signals and constituting part of an A-mode echography device, the therapy apparatus further including means for causing the ultrasound transducer operating in A-mode to transmit a brief signal and receive the echo of the brief signal at the A-mode transducer, means for comparing the echo received with a reference echo, and means for transmitting the result of the comparison to a control device.
According to one advantageous feature, the control device triggers alarm means.
The control device advantageously performs real time closed-loop control of the position of the therapy transducer relative to the patient and in particular, relative to the organ to be treated.
Advantageously, the ultrasound therapy transducer is of the focused type.
According to one preferred feature, both the ultrasound therapy transducer and the A-mode monitoring transducer are integrated into an endocavital probe, in particular a rectal endocavital probe.
In an advantageous embodiment, the focused-type therapy transducer is linked to means for supplying an electronic signal providing variable focusing. The control device preferably provides closed-loop control of the focal length of said therapy transducer as a function of the movements of the patient during the course of therapy.
The therapy apparatus preferably includes means for continuously recording the echoes created by the monitoring transducer operating in A-mode. The A-mode electronic circuit may include an echography device operating in A-mode.
Other advantageous embodiments will also become evident from the description that follows that relates to the therapy apparatus and from the examples and drawings which constitute an integral part of this disclosure.
It will be seen that the invention makes it possible to monitor the position of a patient during therapy in a simple, accurate and reliable fashion, thus resolving the technical problems discussed above, as well as providing other technical advantages which will be evident to those skilled in the art.